How long are biodiversity patterns taking to reach equilibrium under neutral theory

What is it about?

In order to make sense of the natural world, scientists often resort to analysing the equilibrium conditions of the system they study. Biology is no exception and under the controversial but informative neutral theory of biodiversity, the systems are almost invariably assumed to have reached equilibrium. In our paper, we pay close attention, instead, to the time it takes for various patterns of biodiversity to approach equilibrium. We show that even in terms of species richness, some systems on earth, like boreal forests, are unlikely to have reached stasis. For other biodiversity patterns taking even longer to reach equilibrium, our results caution ecologists against assuming equilibrium biodiversity. When one does so, an intermediate mode of speciation is shown to mimic realistic patterns of macroevolution, something that neutral theory was though previously incapable of achieving. Despite some little niggles, the neutral theory of biodiversity continues to surprise us and offers a parsimonious explanation for large scale patterns of biodiversity, especially if one stops assuming equilibrium.

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Why is it important?

Whether biodiversity on earth is limited and has reached a ceiling is a fundamental question in biology. The Neutral Theory of Biodiversity typically assumes that this ceiling has been reached. We show instead that it is unlikely to be the case and should not be the default assumption. Biodiversity patterns can be better described and interpreted if one stop assuming biotas are necessarily at equilibrium.

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